This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this project is to define the role played by a gene termed FXYD1 in the neuropathology of Rett syndrome. Rett syndrome (RTT) is an X-linked neurodevelopmental disorder linked to heterozygous de novo mutations in the MECP2 gene. In the absence of MECP2, the FXYD1 gene is overexpressed in both humans and Mecp2-null mice. FXYD1 encodes a transmembrane modulator of Na+, K+-ATPase activity. These and other observations suggest that FXYD1 is a MeCP2 target gene whose derepression may directly contribute to RTT neuropathogenesis. This project is using a combination of behavioral, morphological and electrophysiological strategies to determine if the absence of FXYD1 is able to rescue RTT-like phenotypes displayed by MeCP2-deficient mice.